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Domoic Acid Poisoning

Domoic acid has been responsible for several deaths and both permanent
and transitory illness in over a hundred people. The toxin is produced
by marine diatoms which are members of the genus Pseudo-nitzschia.
Both shellfish and fish can accumulate this toxin without apparent ill
effects; however, in humans the toxin crosses into the brain and interferes
with nerve signal transmission. People poisoned with very high doses
of the toxin can die, while lower doses can cause permanent brain damage
(short term memory loss). When this toxin was discovered in certain
West coast fish and shellfish, both recreational and commercial fisheries
were briefly closed. This closure, though relatively short, had serious
economic impacts on those communities dependent on these fisheries.

Harmful effects of Domoic Acid

Domoic
Acid

The first reported outbreak of domoic acid poisoning occurred in 1987 when shellfish
from Prince Edward Island Canada were consumed. In that outbreak, 3 people
died and over 100 people developed various toxic symptoms. Domoic acid was found to be produced by the diatom Pseudo-nitzschia multiseries. The most unusual,
and most serious toxic symptom, was a loss of short term memory--hence
the initial designation of the syndrome in humans as amnesiac shellfish poisoning (ASP). However,
since the toxin has been found in fin-fish and the chemical structure
of the toxin is now known, a more accurate term is Domoic Acid Poisoning.
In 1991, along the beaches of Monterey Bay, CA, dead
and dying seabirds were observed--many of the sick birds displayed unusual
symptoms suggesting a neurological toxin. Examination of the contents
of the dead bird's stomachs revealed high levels of domoic acid. Furthermore,
the birds had been eating anchovies from the bay. In turn, examination
of the anchovy gut contents showed that these fish had been consuming
the diatom called Pseudo-nitzschiaaustralis.
Quick action by state health departments along the west coast of the United
States prevented human illnesses by closures of both recreational and
commercial shellfisheries.

Historical Perspective on Domoic Acid

Kainic
Acid

The early work on domoic acid is closely intertwined with a related
compound, kainic acid and its use as a anthelminthic (a parasite remedy).
These products were found in the Rhodophyta, or red algae,
Chondria armata and Digenea simplex. Initial studies
centered on Digenea, a red alga found in tropical and sub-tropical
waters that has been used for centuries as an anthelminthic (Baslow,
1969; Scheuer, 1973; Scheuer, 1980). Murakami et al. (1953) isolated
the active anthelmintic ingredient and named it digenic acid and then
later renamed it kainic acid (Murakami et al., 1954) after the Japanese
name for the alga--kaininso.

While domoic acid has recently, i.e., in 1987, been found to be toxic
to humans, the compound itself was first isolated in 1959 by Daigo from
Chondria armata and its final structure and stereochemistry
determined in 1966 by Takemoto et al. Domoic acid has also been isolated
from another red algae, Alsidium corallinum, by Impellizzeri
et al. (1975). Dr. Steve Bates, Department of Fisheries and Oceans-Canada, has prepared an extensive bibliography on domoic acid.

For more detailed information about the fascinating history and chemistry
of marine natural products, the volumes by Paul Scheuer in the references
below are highly recommended--these books are part of a larger series
by Dr. Scheuer. In addition, the title by Baslow is also highly recommended,
the author updated his original 1969 book on Marine Pharmacology in
1977, unfortunately both books are out of print but probably available
in university/college libraries.